In the Imperial system, a gallon is a unit of liquid volume equal to 128 fluid ounces, 8 pints, or 16 half pints. A half pint, in turn, is defined as 16 fluid ounces or half a pint. Half pints are commonly used in everyday life, such as in beer glasses or cream containers. Understanding these units of measurement is essential for effective communication and accurate liquid calculations in various industries and settings.